This example doesn't specify a credential and a project intentionally.
$ gcloud auth application-default login
# export GOOGLE_PROJECT=terraform-toshi0607
# 【YOUR PROJECT】をあなたのGCPプロジェクトに置き換えてください。
$ export GOOGLE_PROJECT=【YOUR PROJECT】
$ terraform init
$ terraform plan
$ terraform plan -var="vm_enable=true"
$ terraform apply -var="vm_enable=true"
$ terraform destroy